This is one of the most interesting websites I've come across. I found this when I was learning about the "new money" that recently came out in 2003. You can learn about how coins and currency are made, any updated "new money" that is in the making, and new press releases. You can even subscribe for a free e-newsletter about Currency and Coins in your inbox, if you wish...great for coin collectors and those who are just interested.

U.S. Treasury - Currency and Coins